Dubious debit order practice

Please could someone advise why it shows arrears on my loan account? The debit order goes off each month but on the African Bank statement it shows a reversal and then another payment... there are no reversals. This is obviously some mistake on African Bank's side which is messing with the calculations and now giving arrears interest? The debt also goes off on the wrong day.... I get paid on the last working day of the month but instead it starts searching my account a lot earlier than that.